The current standard of care for patients with significant aortic valve disease is still surgical aortic valve replacement. As the treatment of many cardiovascular diseases has become minimally invasive and catheter-based, endovascular techniques and equipment has led to the development of percutaneous aortic valve (PAV) replacement as a potential clinical reality. PAV replacement is currently an investigational procedure.
The notion of PAV replacement was first introduced in 1992 by Andersen et al. in a swine model [Andersen H R et al., Eur Heart J 1992; 13:704-7081]. The first human implantation of a percutaneous valved-stent was performed in the pulmonic position as reported by Bonhoeffer et al. in 2000 [Bonhoeffer P, et al., Lancet 2000;356:1403-1405]. The first human implantation of a PAV was described in 2002 using a valved-stent design by Cribier et al. via the antegrade/inter-atrial septal puncture approach [Cribier A, et al., Circulation 2002;106(24):3006-3008]. Other techniques such as retrograde and transapical approaches of delivery and deployment of the PAV were later introduced [Webb J G, et al., Circulation 2006;1 13:842-850; Lichtenstein S V, et al., Circulation 2006;114(6):591-596].
Notwithstanding early inroads, the percutaneous approach to aortic valve replacement is challenged by multiple key issues that currently frustrate the success of the procedure. It remains an investigational procedure rather than mainstay therapy for many patients who may be benefited. Significant obstacles include accurate placement of the PAV at the aortic annulus to avoid damaging important adjacent structures and vascular complications resulting from the large size delivery system.
In the PAV replacement procedure, most of the cardiac complications occur at the required precise placement of the PAV during implantation. Due to the aortic valve's close proximity to the coronary ostia on one side, and the mitral valve on the other, misalignment of the PAV can cause serious compromise of coronary or mitral valve function [Boudjemline Y, et al., Circulation 2002;105(6):775; Ferrari M, et al., Heart 2004;90(11):1326-1331]. The significant hemodynamic forces encountered at the left ventricular outflow tract to the ascending aorta, together with the anatomic structures comprising the diseased native valve, add to the difficulty of precise placement of the PAV and the risk of device embolization.
Percutaneous aortic valve replacement bears analogy to percutaneous coronary intervention (PCI) of complicated left main stenosis in the high risk nature and potential for patient instability. In patients with complex coronary disease and high risk factors, the operator has the option to support the hemodynamics by inserting an intra-aortic balloon pump (IABP) [Mishra S et al., Am J Cardiol 2006;98(5):608-612]. Current investigational systems do not possess similar capabilities for prophylactic protection and hemodynamic support for those performing PAV procedures.
Vascular complications also result from the large size of currently available PAV delivery systems. The large French size catheter systems currently in use to deliver replacement valves percutaneously have the potential to cause significant injuries. [Boudjemline Y, et al., Circulation 2002;105(6):775; Ferrari M. et al., Heart 2004;90(11):1326-1331; Grube E, et al., J Am Coll Cardiol 2007;50:69-76; Hanzel G S, et al., Catheter Cardiovasc Interv 2005;64(3):322-32]. The diameter of the PAV delivery catheter system must be reduced in order for the procedure to become safe and routine.
Objects of the present invention include providing a PAV delivery and deployment system that demonstrates structural integrity and that includes specific features to optimize precise PAV placement and deployment while maintaining patient stability. Precise PAV placement and deployment can be facilitated by removing anatomic structures that can hinder or interfere with precise PAV placement, and by minimizing the hemodynamic forces on the devices encountered by the surgeon during the PAV replacement procedure. Maintaining patient stability during the replacement procedure can be facilitated by providing a substitute valve that promotes coronary perfusion while moderating stresses (aortic insufficiency and aortic stenosis) experienced by cardiac muscle prior to the PAV becoming operational.
Further objects of the present invention include providing a PAV delivery system demonstrating a significantly reduced French size to minimize the risk of vascular injuries consequent to the PAV delivery procedure.